MCQs on DC motor

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 1. In a DC motor the direction of rotation is determined by
(a) Lenz law.
(b) Faraday Law.
(c) Fleming left hand rule.
(d) Fleming right hand rule.   

 2. DC motor can be easily identified by looking at
(a) frame.
(b) commutator.
(c) winding.
(d) yoke.   

 3. The main function of using starter in DC motor is to
(a) provide starting torque.
(b) reduce starting losses.
(c) limit starting current.
(d) limit the speed.   

 4. Which of the following instrument is used to measure the speed of DC motor?
(a) Barometer.
(b) Tachometer.
(c) Anemometer.
(d) Multimeter.    

 5. The direction of rotation of a dc shunt motor can be reversed by interchanging
(a) the supply terminal.
(b) the field terminal only.
(c) the armature terminal only.
(d) either field or armature terminals.  

 6. In a DC motor, unidirectional torque is produce with the help of
(a) slip rings.
(b) commutator.
(c) starter.
(d) thyristor control.   

 7. Which of the following starter is mainly used for the protection of DC series motor?
(a) Two point starter
(b) Three point starter
(c) Four point starter
(d) None of the above  

 8. If the flux of a dc motor approaches zero, its speed will
(a) approach infinity.
(b) approach zero.
(c) remain unchanged.
(d) none of the above.   

 9. When the voltage of a DC shunt motor is reduced by half, the speed of motor will be
(a) one fourth.
(b) half.
(c) remain same.
(d) double.   

 10. When two DC series Motors are connected in parallel, the resultant speed is
(a) zero.
(b) decreases.
(c) remain same.
(d) increases.    

 11. When the back EMF and the speed of DC shunt Motors both are double, the torque devolved by the motor will
(a) remain same.
(b) reduced by four time.
(c) reduced by half.
(d) increased by four time.  

 12. If the field winding of a dc shunt motor running at light load gets opened, the motor will
(a) burn.
(b) stop.
(c) make noise.
(d) pick up high speed.  

 13. The main purpose of using field regulator in a DC compound motor is to
(a) provide constant voltage.
(b) limit the current.
(c) reduce losses.
(d) control the flux.    

 14. Which of the following method of braking is used in Rolling Mills?
(a) Plugging.
(b) regenerative braking.
(c) dynamic braking.
(d) mechanical braking.    

 15. The armature resistance of the DC motor is nearly equal to
(a) 0.05 ohm.
(b) 0.5 ohm.
(c) 50 ohm.
(d) 105 ohm.   

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